electron - an elementary particle with negative chargedelta ray - an electron ejected from matter by ionizing radiation free electron - electron that is not attached to an atom or ion or molecule but is free to move under the influence of an electric field lepton - an elementary particle that participates in weak interactions; has a baryon number of 0 photoelectron - an electron that is emitted from an atom or molecule by an incident photon valence electron - an electron in the outer shell of an atom which can combine with other atoms to form molecules |